1. Field of the Invention
This invention relates to controllable overrunning coupling assemblies especially for use in vehicular automatic transmissions.
2. Background Art
A typical one-way clutch consists of an inner ring, an outer ring and a locking device between the two rings. The one-way clutch is designed to lock in one direction and to allow free rotation in the other direction. Two types of one-way clutches often used in vehicular, automatic transmissions include:                Roller type which consists of spring loaded rollers between the inner and outer race of the one-way clutch. (Roller type is also used without springs on some applications); and        Sprag type which consists of asymmetrically shaped wedges located between the inner and outer race of the one-way clutch.        
The one-way clutches are typically used in the transmission to prevent an interruption of drive torque (i.e., power flow) during certain gear shifts and to allow engine braking during coasting.
FIG. 1 illustrates a prior art mechanical diode (i.e., MD) clutch controllable with a slide plate in a transmission. The clutch replaces a L/R friction pack and functions as a one-way clutch (OWC) and as a backing plate. The automatic transmission gear system includes a planetary gearing arrangement 10, which comprises three simple planetary gear units 12, 14 and 16. Gear unit 12 includes a sun gear 18, a ring gear 20, and a planetary carrier 22. Gear unit 14 comprises a sun gear 24, a ring gear 26, and a planetary carrier 28. Gear unit 16 comprises a sun gear 30, a ring gear 32, and a planetary carrier 34.
Carrier 28 is drivably connected to gear 32, as shown at 36. Carrier 22 is drivably connected to ring gear 26, as shown at 38. Ring gear 20 is drivably connected to planetary carrier 34 by a torque transfer member 40.
A torque input shaft, which corresponds to the turbine shaft of a hydrokinetic torque converter (not shown), is designated by reference numeral 42. It is splined to sun gear 24. Torque output sleeve shaft 44 is splined to carrier 34, and carrier 22 is splined to friction clutch element 46 of a multiple disc clutch assembly 48, which is engaged during operation of the transmission in the fourth, fifth and sixth speed ratios.
Clutch plates register with clutch discs of the clutch assembly 48. Clutch plates are connected to clutch member 50, which defines in part spaced annular clutch cylinders, as shown at 52 and 54. An annular piston 56 is disposed in clutch cylinder 52 and an annular piston 58 is disposed in annular cylinder 54. The pistons 56 and 58 are biased to a clutch release position by clutch return springs 60 and 62, respectively. The cylinder 52 and the piston 56 define a pressure chamber, which, when pressurized causes piston 56 to frictionally engage the clutch plates and clutch discs of the multiple disc clutch assembly 48 to establish a driving connection between carrier 22 and clutch element 50.
Internally splined clutch plates of a multiple disc clutch assembly 64 are splined to the clutch element 50. Externally splined clutch plates of multiple disc clutch assembly 64 are drivably connected to sun gear 18 by clutch element 66.
Clutch element 66 is connected drivably to friction brake discs 68, which register with friction plates 70 of a multiple disc brake assembly 72.
Clutch disc assembly 64 is engaged during operation in the third and fifth speed ratios, as well as in reverse drive. Brake disc assembly 72 is engaged during operation in second ratio and sixth ratio.
The stationary transmission housing 74 rotatably supports turbine shaft 42, as shown at 76. Housing 74 defines an annular brake pressure chamber 78 in which is situated annular piston 80. A brake actuator element 82 carried by the piston 80 is engageable with the brake disc assembly 72 to establish a torque reaction point for sun gear 18.
Sun gear 16 is drivably connected to brake disc assembly 84 by means of torque transfer element 86. Housing 74 defines an annular cylinder 88, which receives annular piston 90.
A planar clutch assembly of the prior art is illustrated in FIG. 1 at 92. The assembly 92 comprises a notch plate 94, which envelopes pocket plate 96. A planar annular surface 98 of the assembly 92 provides a brake disc reaction surface, which is engaged by an adjacent brake disc of the brake disc assembly 84. Clutch plates of the brake disc assembly 84 are externally splined to the transmission housing 74.
The surface 98 on the notch plate 94 is fully precision ground prior to assembly so that it can act as a backing plate for the friction disc pack. It thus is not necessary with the design illustrated in FIG. 1 to provide a separate backup plate for the friction brake assembly. The integrated design illustrated in FIG. 1 incorporates common features for the planar clutch assembly 92 and the friction brake assembly 84, thereby eliminating components and reducing the packaging space for the torque transmitting elements of the transmission.
The brake disc assembly 84 is frictionally engaged when pressure is applied by the piston 90, which actuates pressure plate 102 of the brake disc assembly 84.
The notch plate 94 acts as the reaction element for the brake disc assembly 84. It is splined to the transmission housing 74 and is secured within the transmission housing against axial displacement by snap ring 106 located in a snap ring groove in the transmission housing 74.
The pocket plate 96 is held fast within the notch plate 94 by a snap ring 104 situated in a snap ring groove formed in the pocket plate 96. An annular thrust plate 107 is located axially along the rotational axis between the pocket plate 96 and the snap ring 104. The thrust plate 107 has a first axial face that contacts the snap ring 104 and has a second axial face oriented in the opposite axial direction as the first axial face and contacting only the pocket plate 96 without contacting the notch plate 94. Furthermore, the thrust plate 107 has a retainer (not shown) projecting therefrom to prevent rotation of the thrust plate. Pocket plate 96 has an axial extension 116 which has splines 108 to establish a splined driving connection to carrier 22. The integral design illustrated in FIG. 1 also eliminates a L/R friction pack or multiple disc brake assembly which includes friction brake discs that would normally be splined to the extension 116.
The planar one-way clutch assembly 92 also includes (as shown, for example, in U.S. Pat. Nos. 7,258,214 and 7,344,010 and published U.S. patent application 2007/0056825) forward and reverse sets of pawls or keys (not shown) and a planar control number or plate 109 which is rotatable between facing surfaces of the pocket plate 96 and the notch plate 94 by means of a slide plate fork 111 to move the pawls or keys between notch-engaging and notch-disengaged positions.
U.S. Pat. No. 5,927,455 discloses a bi-directional overrunning pawl-type clutch having a driving member mounted for power rotation, a driven member mounted for rotation adjacent the driving member, with each of the driving and driven members having pawl engaging shoulders, and a plurality of rigid pawls interposed between the driving and driven members. A control element is mounted for shifting movement between the driving and driven members to control the position of the pawls which are yieldably biased toward positions of engagement extending between the driving and driven members to produce driving engagement therebetween. The control element is shiftable to various positions to permit driving and overrunning in one direction or driving and overrunning in the opposite direction dependent upon the direction of rotation of the driving member.
U.S. Pat. No. 6,244,965 discloses a planar overrunning coupling for transfer of torque from a driving member to a driven member in one direction and which permits freewheeling motion between the members upon a torque reversal. The coupling includes coupling plates situated in close proximity with a strut retainer plate disposed between them, one plate being connected to the driving member and the other plate being connected to the driven member, each plate having strut recesses, a series of struts located in the recesses of one plate so that each strut may be pivoted, thereby allowing the struts to engage the companion recesses in the other coupling plate. The retainer has angularly spaced apertures that register with the struts to permit pivotal movement of the struts when the retainer plate is in one rotary position. The retainer plate, when it is in a second rotary position, prevents pivotal motion of the struts, thereby permitting freewheeling relative motion of the coupling plates.
U.S. Pat. No. 6,290,044 discloses a selectable one-way clutch assembly for use in an automatic transmission comprising a strut plate rotatable about a central hub and having pockets and struts mounted therein for pivotable rotation. A selecting plate concentrically located about an activator hub has teeth extending axially inboard and configured to fit in the apertures in an activator plate. A turning device is selectively operable to activate one-way clutching mode by rotating the pin of a control plate to disengage selecting cams and displace selecting plate teeth inboard beyond the inboard face of the activator plate wherein the struts catch the teeth when the strut plate assembly is rotated in a clutching direction. The catching ends of the struts are cammed in the pockets by ramped camming ends of the teeth when the strut plate assembly is rotated in the opposing direction, thereby allowing freewheeling of the strut plate in the overrun direction.
U.S. Pat. No. 7,258,214 discloses an overrunning coupling assembly and a method of controlling the engagement of planar first and second members wherein two sets of opposed engaging struts are applied with one motion of a single control plate or member. The planar first and second members have inside surfaces extending generally normal to a first axis. The assembly includes free-floating, forward keys and free-floating, reverse keys opposed to the forward keys. The forward and reverse keys are movable between a notch-engaging, engaged position and a disengaged position in which the second member is permitted to free-wheel relative to the first member. The planar control member is disposed between the first and second surfaces and is controllably rotatable about the first axis between first and second angular positions relative to the first member.
U.S. Pat. No. 7,344,010 discloses an overrunning coupling assembly and a method of controlling the engagement of planar first and second members wherein the assembly includes clustered pawls and their respective pawl-holding portions. The planar first and second members have inside surfaces extending generally normal to a first axis. The pawls include a forward set of free-floating pawls and a reverse set of free-floating, clustered pawls. The forward and reverse sets of pawls are movable between a notch-engaging, engaged position and a disengaged position. Because of the clustering, a control element, disposed between the first and second surfaces, need not be fully circular and is controllably rotatable about the first axis between first and second angular positions relative to the first member.
Published patent application US 2006/0278487 discloses an overrunning radial coupling assembly or clutch and a method of controlling the engagement of inner and outer plates or members of the assembly wherein adjacent engaging radial locking pawls are selectively controlled by a single, rotatable control plate or element to obtain full lock, one-way lock and one-way overrun conditions. The assembly includes free-floating, forward pawls and free-floating, reverse pawls adjacent to their respective forward pawls. The forward and reverse pawls are movable between a notch-engaging, engaged position (i.e., full lock condition) and a disengaged position in which the outer member is permitted to free-wheel relative to the inner member in the one-way overrun condition in one direction about a first axis and the outer member is locked to the inner member in the one-way lock condition in the opposite direction. A number of different embodiments of the assembly and method are provided.
Other related U.S. patent publications include U.S. 2005/0279602; 2006/0021838; 2006/0185957; 2007/0062775; 2007/0056825; 2007/0131509 and 2008/0185253 and the following U.S. patents:
U.S. Pat. Nos. 7,455,157; 7,455,156; 7,451,862; 7,448,481; 7,383,930; 7,296,668; 7,223,198; 7,100,756; 6,854,577; RE 38,498; 6,571,926; 6,505,721; 6,481,551; 6,386,349; 6,333,112; 6,193,038; 6,186,299; 6,129,190; 6,125,980, 6,116,394; 6,065,576; 5,964,331; 5,918,715; and 5,871,071.
One problem associated with the prior art selectable or controllable one-way clutches, is that a control plate or element is used to contain or control both forward and reverse struts in a stationary pocket plate. Consequently, a relatively large quantity of lubricating fluid or oil is required to dampen the forward struts during overrun.
For purposes of this application, the term “coupling” should be interpreted to include clutches or brakes wherein one of the plates is drivably connected to a torque delivery element of a transmission and the other plate is drivably connected to another torque delivery element or is anchored and held stationary with respect to a transmission housing. The terms “coupling,” “clutch” and “brake” may be used interchangeably.